[Tomaso]

Hi Guys,
Newbie here. As my first post I mentioned I had just purchased a 66 Pontiac Bonneville. It currently has a 389. I would like a beefier engine. What would be the best route to take? I heard some 389s were good motors.
Should I:

Keep the 389 and get a stroker kit?
Or aim for a 400/455 with a stroker kit?


Mike

[389]

I would keep the 389. I went down this road with a 64. I changed the 389/4 speed hydro to a 462/th400. the motor had ported 6X heads and a 041 cam. The car ended up being a pain in the ass, it was loud, smelly and sucked gas like crazy. I was always trying to rev it up into the power band that cam was so wrong for a street car with this weight. Frankly it didn't go much faster then when it had the 389. I would put a 068 cam in that 389 and play around with the timing. Keep the points and use it to trigger a CD box like the MSD6AL. Look for a nice 3.08 rear end with a dual quad intake and run two Carter AFBs on it.. Remember its a Bonneville not a GTO..

[Holeshot71]

Originally Posted by 389

I would keep the 389. I went down this road with a 64. I changed the 389/4 speed hydro to a 462/th400. the motor had ported 6X heads and a 041 cam. The car ended up being a pain in the ass, it was loud, smelly and sucked gas like crazy. I was always trying to rev it up into the power band that cam was so wrong for a street car with this weight. Frankly it didn't go much faster then when it had the 389. I would put a 068 cam in that 389 and play around with the timing. Keep the points and use it to trigger a CD box like the MSD6AL. Look for a nice 3.08 rear end with a dual quad intake and run two Carter AFBs on it.. Remember its a Bonneville not a GTO..

What kind of compression were you running? Sounds like something may have been off with your tune or combination of parts. A 455 with ported heads and 041 cam should run STRONG from idle to the rev limiter if set up properly

[ZeGermanHam]

Originally Posted by 389

I would keep the 389. I went down this road with a 64. I changed the 389/4 speed hydro to a 462/th400. the motor had ported 6X heads and a 041 cam. The car ended up being a pain in the ass, it was loud, smelly and sucked gas like crazy. I was always trying to rev it up into the power band that cam was so wrong for a street car with this weight. Frankly it didn't go much faster then when it had the 389. I would put a 068 cam in that 389 and play around with the timing. Keep the points and use it to trigger a CD box like the MSD6AL. Look for a nice 3.08 rear end with a dual quad intake and run two Carter AFBs on it.. Remember its a Bonneville not a GTO..

This just sounds like the 462 was comprised of the wrong components for your desired application.

[Tomaso]

Thanks for the info! What about the cylinder heads? Keep stock and rebuild them? Or go with aftermarket?

[Rob in NH]

What about a set of 093 heads for a 389?

[dmac]

Originally Posted by Tomaso

Thanks for the info! What about the cylinder heads? Keep stock and rebuild them? Or go with aftermarket?

What are you going to do with the car? For cruising, you don't need anything but stock heads. If you are going to regularly see over about 4500 rpm, you might want aftermarket heads or just upgrade what you have. Just remember your budget- too much power and you start breaking things, and then need to upgrade those. If everything else is done on the car and the way you want it- paint, interior, suspension, etc, go for it. But if you start adding power, and the trans isn't upgraded, and the suspension, and the brakes, and if you don't have an unlimited budget, you can easily start down a road where you will never drive your car because you will always be fixing it. The cars came out of the factory with equipment made to handle what power the motor made.

[Tomaso]

I would like it a street cruiser. Not using it for drag racing. Just street. But would like the torque to be there when needed...

[77 TRASHCAN]

Yes a 389 will do the job well!
There’s a guy in Western Canada, SDPerformance. He would be great to work over your heads. He has a website, he can be difficult to contact, but is worth the effort. The website is SD Perfo

[ta man]

A 455 would be a great choice as a mild build. Readily available 6x heads..flat tappet cam..good power lots of torque.
As far as sourcing a rebuilt shortblock or complete engine..put wanted ads out on Kijiji, Craiglist..or other marketplaces. Many guys are sitting on shortblocks for projects..but will never use them and will sell them. The other way is buying a complete one.but as a fellow Canadian..our dollar really drives up the cost.

[chiphead]

Since the car is new to you, I suggest driving it and enjoying it awhile. Figure out what it needs, and what you want to retain. Lots of guys have built big HP engines and then been disappointed when they can't use the power because they never shook the rest of the car out.

My car has been apart for years and I wish I could just drive it, at any HP level.

[Stuart]

Originally Posted by chiphead

Since the car is new to you, I suggest driving it and enjoying it awhile. Figure out what it needs, and what you want to retain. Lots of guys have built big HP engines and then been disappointed when they can't use the power because they never shook the rest of the car out.

My car has been apart for years and I wish I could just drive it, at any HP level.

This is what I'd do, unless you're anxious to spend a bunch of money. A stock 389 in good shape and good tune is no slouch, and should work pretty well for a street cruiser.

[carbking]

Originally Posted by chiphead

Since the car is new to you, I suggest driving it and enjoying it awhile. Figure out what it needs, and what you want to retain. Lots of guys have built big HP engines and then been disappointed when they can't use the power because they never shook the rest of the car out.

My car has been apart for years and I wish I could just drive it, at any HP level.

My vote also. A 389 is no slouch engine. Drive it awhile, and then if you decide you just can't live without more "go" then go for it.

Oh, and while I am sure I am the exception here, my GTO was apart for 28 years before I got it back together! Life happens! Ones priorities change in 28 years! And yes, I did build a performance engine. One change begets 6 more changes, each of which begets 6 more changes each of which................................

Jon.

[Tomaso]

That's great!! I found their website and added it to my favourites so I can contact them later on.
Thanks again!

[b-man]

Go with the 455 for the best street engine if torque is what you’re after.

A bone stock 455 will make you smile, and will be less expensive than a hotrodded 389.

Both engines are great and have their place, but on the street cubic inches gets the job done without the need for ported heads and big cams.

Another thing to be aware of is 1966 389 blocks are not known for their strength and are also known for having very thin cylinder walls, I would avoid building a hot engine using that block.

A big Bonne needs a big engine, you won’t be sorry going with a mild 455. In later years (1969 for example) the 428 became the standard Bonneville power plant while all the other big Pontiacs came with the 400.

[SRR]

Originally Posted by b-man

Go with the 455 for the best street engine if torque is what you’re after.

A bone stock 455 will make you smile, and will be less expensive than a hotrodded 389.

Both engines are great and have their place, but on the street cubic inches gets the job done without the need for ported heads and big cams.

Another thing to be aware of is 1966 389 blocks are not known for their strength and are also known for having very thin cylinder walls, I would avoid building a hot engine using that block.

A big Bonne needs a big engine, you won’t be sorry going with a mild 455. In later years (1969 for example) the 428 became the standard Bonneville power plant while all the other big Pontiacs came with the 400.

Big cars like 455 engines...makes them act like "A" bodies.

[goatwgn]

Originally Posted by b-man

Go with the 455 for the best street engine if torque is what you’re after.

A bone stock 455 will make you smile, and will be less expensive than a hotrodded 389.

Both engines are great and have their place, but on the street cubic inches gets the job done without the need for ported heads and big cams.

Another thing to be aware of is 1966 389 blocks are not known for their strength and are also known for having very thin cylinder walls, I would avoid building a hot engine using that block.

A big Bonne needs a big engine, you won’t be sorry going with a mild 455. In later years (1969 for example) the 428 became the standard Bonneville power plant while all the other big Pontiacs came with the 400.

I agree, wholeheartedly on this approach. Literally, the best combination for your car would be a 9.0 to 1 compression 455, with an 068 cam, 1968-71 Q jet intake and carb, HEI ignition, cast iron manifolds, TH400 with a 3.08 rear end. Build, close the hood, pile on the miles.

[64speed]

No replacement for displacement BUT with that being said the 389 in your Bonneville should at least take a .30 overbore and even without a stroker kit will put a smile on your face if built properly. I had a chance to buy a Mint 66 Bonneville in 2002 back before the car boom. Car was perfect and had power windows and AC the whole 9 yards. I went and drove it and told the man I would be back the next afternoon with cash. The asking price was 5500 bucks. Before I could get there the asshole sold it to a 17 year old kid who drove it for about 2 weeks before hitting a light pole in a grocery store parking lot.

[hurryinhoosier62]

The problem with ‘66 389 blocks is there seems to be a wide variance in cylinder wall thickness. I personally know of two that had cylinder walls of .090 or LESS. If you’re going to use the original block have it ultrasonic tested before boring. A 3” main 4 inch stroke crank along with a .060 overbore will give you a 428 engine. Nothing wrong with the performance of a 428.....A .030 overbore with the same 4 inch stroke crank gives you a 421. The biggest question is how large is your budget. Around here, 455s is scarce while 400s/389s are far more plentiful.

[Dragncar]

66 389s had thin cylinder walls. Over heated a lot. There were plenty of come backs to the dealers back then.